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The pilot of a C501 equipped with a garmin 430 descended on an ILS to visual ground contact with an incorrect mode switch selection disabling GS.
| Attributes | |
| ACN | 683636 |
| Time | |
| Date | 200512 |
| Local Time Of Day | 0601 To 1200 |
| Place | |
| Locale Reference | airport : jwn.airport |
| State Reference | TN |
| Altitude | agl single value : 600 |
| Environment | |
| Flight Conditions | IMC |
| Light | Daylight |
| Aircraft 1 | |
| Controlling Facilities | tracon : bna.tracon |
| Operator | general aviation : corporate |
| Make Model Name | Citation I/SP |
| Operating Under FAR Part | Part 91 |
| Navigation In Use | other |
| Flight Phase | descent : approach |
| Flight Plan | IFR |
| Person 1 | |
| Affiliation | company : corporate |
| Function | flight crew : single pilot |
| Qualification | pilot : atp |
| Experience | flight time last 90 days : 45 flight time total : 6500 flight time type : 3500 |
| ASRS Report | 683636 |
| Person 2 | |
| Affiliation | government : faa |
| Function | controller : approach |
| Events | |
| Anomaly | altitude deviation : crossing restriction not met altitude deviation : undershoot non adherence : published procedure non adherence : far other spatial deviation |
| Independent Detector | other flight crewa |
| Resolutory Action | none taken : anomaly accepted |
| Supplementary | |
| Problem Areas | Aircraft Flight Crew Human Performance |
| Primary Problem | Flight Crew Human Performance |
Narrative:
During ILS DME approach GS indication stayed at top of indicator; so I continued as a localizer only procedure to minimums. The ceiling was lower (about 600 ft) than AWOS reported. After becoming visual; the airport was at my 1 O'clock position and about 1/2 mi. I continued over the airport; made 180 degree turn and landed to the north. Circles were not approved. I had about 2 hours in this airplane and was not fully familiar with the garmin 430 but had expected to have 1000 and 3 for the approach. When I broke out of cloud with airport off center and not able to receive GS; I decided it might be safer to land and I was also familiar with towers around airport. Later I found out the unit was in GPS obs mode. Most citations I have flown have a switch separate from GPS for switching from GPS and navigation. Also; most switch when localizer frequency is dialed in. I am glad I had increased my personal minimums for the first few trips in this aircraft since at this airport the WX went down below forecast.
Original NASA ASRS Text
Title: THE PLT OF A C501 EQUIPPED WITH A GARMIN 430 DSNDED ON AN ILS TO VISUAL GND CONTACT WITH AN INCORRECT MODE SWITCH SELECTION DISABLING GS.
Narrative: DURING ILS DME APCH GS INDICATION STAYED AT TOP OF INDICATOR; SO I CONTINUED AS A LOC ONLY PROC TO MINIMUMS. THE CEILING WAS LOWER (ABOUT 600 FT) THAN AWOS RPTED. AFTER BECOMING VISUAL; THE ARPT WAS AT MY 1 O'CLOCK POS AND ABOUT 1/2 MI. I CONTINUED OVER THE ARPT; MADE 180 DEG TURN AND LANDED TO THE N. CIRCLES WERE NOT APPROVED. I HAD ABOUT 2 HRS IN THIS AIRPLANE AND WAS NOT FULLY FAMILIAR WITH THE GARMIN 430 BUT HAD EXPECTED TO HAVE 1000 AND 3 FOR THE APCH. WHEN I BROKE OUT OF CLOUD WITH ARPT OFF CTR AND NOT ABLE TO RECEIVE GS; I DECIDED IT MIGHT BE SAFER TO LAND AND I WAS ALSO FAMILIAR WITH TWRS AROUND ARPT. LATER I FOUND OUT THE UNIT WAS IN GPS OBS MODE. MOST CITATIONS I HAVE FLOWN HAVE A SWITCH SEPARATE FROM GPS FOR SWITCHING FROM GPS AND NAV. ALSO; MOST SWITCH WHEN LOC FREQ IS DIALED IN. I AM GLAD I HAD INCREASED MY PERSONAL MINIMUMS FOR THE FIRST FEW TRIPS IN THIS ACFT SINCE AT THIS ARPT THE WX WENT DOWN BELOW FORECAST.
Data retrieved from NASA's ASRS site as of January 2009 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.